really nice, i d do the following:
auto-activating a respawn platform costs 3 coins.
death looses 10 coins.
This would add a nice motivator to collect these coins as well as avoiding death!

Why would I suggest this? Because, I collected all coins only in the first level. After seeing that they served no real ingame purpose I only collected them if they were directly in my way, or really easy (without dieing) to collect. Using them to activate the respawners would allow the player to play the game without the fear of "loosing all lives", but maintain the fear of not beeing able to activate a further platform.

Also, this way coins could be used as some kind of "health bar" in more advanced levels. Some "intelligent" enemies could act as thieves, stealing coins from you, instead of killing you on the spot.

Last but not least a nicer world map than the stoopid every-standard-game-of-this-type-has-it 1|2|3|... setup would be nice, with multiple levels beeing reachable from the first and so on. This is where your total coins collected could come in handy: as an entrance fee to unlock a level. I strongly recommend here not to make the last secret level you might want to add require a pure 100% coins collected, almost noone would try it, then. 50% of coins collectable would be fair enough for that ;)